a. Field of the Invention
This invention relates to a turntable unit and more especially to a turntable unit adapted to support construction equipment, for example, a drilling assembly.
B. Description of Prior Art
In order to carry out operations in outlying areas in which a varied terrain is encountered such as in mining and road making, construction assemblies are mounted on a vehicle which must be capable of travelling over the varied terrain. Vehicles which will meet the arduous requirements in one respect have frequently failed in other respects. Generally, the vehicles which are used to mount working assemblies are of the track type being mounted on caterpillar tracks and are large in size and heavy in weight.
An example of such a construction assembly is a rock drill used for boring holes. Such rock drills may include a pneumatic drill mounted on a guide rail which is supported on a rotatable boom assembly; the boom assembly being mounted on the vehicle.
Suitably the boom assembly may be mounted on a rotatable turntable on the vehicle to allow the operator to select a plurality of directions for feeding the drill to the work area. The turntable may also support a cabin for the operator.
The turntable has to be a rugged component to support the heavy load of the drill assembly or other construction assembly and the operator's cabin; and also to withstand the continuous vibrations which occur in operation. The turntable is therefore generally a massive component.
In view of the nature of the construction equipment mounted on the turntable and so that the operator may operate the vehicle safely and drive it from place to place it is desirable to avoid free rotation of the turntable with its mounted components when the vehicle is travelling or working.
In conventional systems the braking action of the gears through which the turntable is driven has been used to prevent free rotation. However, while the free rotation is largely avoided in this way there is still some free play or slack in view of the rugged, unsophisticated gear assemblies used; the resulting small movements of the turntable result in wear on the gears.